import java.util.List;

public class ReverseLinkedList {
    /**
     * 给你单链表的头节点 head ，请你反转链表，并返回反转后的链表。
     * @param head
     * @return
     */
    public ListNode reverseList(ListNode head) {
        ListNode pre = null;
        ListNode cur = head;
        while (cur!=null){
            ListNode next = cur.next;
            cur.next = pre;
            pre =cur;
            cur = next;
        }
        return pre;


    }
}
